Time periods or blood periods or school periods.
New Guinea is administratively divided into two parts: its western half comprises the Indonesian propinsi (or provinsi; provinces) of Papua and West Papua (collectively, formerly called Irian Jaya); and its eastern half comprises the major part of Papua New Guinea, an independent country since 1975.
Answer:
The celestial sphere is a fictional sphere to which all celestial objects can be projected.
Explanation:
At any time an observer can see only the half of celestial sphere because the other half lies under the horizon. The celestial sphere is the medium used for sphere astronomy. The celestial sphere does not have a defined magnitude. It can be infinite or at least really big.
The Earth's atmosphere is mostly Nitrogen ~ 78% and Oxygen ~21% gas.
